OKLAHOMA CITY (AP) — Oklahoma GOP U.S. Rep. Markwayne Mullin says he’ll run for the U.S. Senate seat that is coming open after Sen. Jim Inhofe’s surprise announcement that he’s retiring before his term is up.

Mullin said in a video message Saturday that he planned to enter the race, as expected political shake-ups begin. Mullin is a plumbing company owner and citizen of the Cherokee Nation.

He’s currently serving his fifth term representing Oklahoma’s 2nd Congressional District. Republican state Sen. Nathan Dahm also announced Monday that he’s running for Inhofe’s seat.

Inhofe on Friday announced his endorsement of his chief of staff, Luke Holland, who is also running for the seat.